check_msg.c: make open_tmp_file not static
check_msg.c: make open_tmp_file not static

The pack unit tests will need to have a way to create a
temporary file. Allowing them to use open_tmp_file is
simpler.

git-svn-id: d023f1085a36f7a677188d00334e37d38ffecf51@963 64e312b2-a51f-0410-8e61-82d0ca0eb02a

9fcc/check,libcheck/check,brarcher/check,brarcher/check,krichter722/check,brarcher/check,libcheck/check,libcheck/check,brarcher/check,krichter722/check,libcheck/check,krichter722/check,libcheck/check,krichter722/check,9fcc/check,9fcc/check,krichter722/check,9fcc/check,brarcher/check,9fcc/check